The long term objective is to advance our understanding of the role of metallothionein in the etiology of certain types of cancer. Hepatocellular carcinoma (HCC) is the fifth most prevalent cancer in the world and is third leading cause of cancer related death in the Western hemisphere. A common characteristic of the liver carcinogens is induction of oxidative stress by inflammatory cells resulting in chronic hepatic injury that leads to transformation of regenerating hepatocytes. Scavenging of the reactive oxygen species (ROS) by antioxidants is, therefore, crucial for prevention of oxidative damage to cells that causes cancer. Metallothioneins (MT) are potent antioxidants that protect cells from deleterious effects of ROS whereas MT null cells are sensitive to xenobiotics that generate free radicals. Liver is abundant in both major isoforms of MT (MT-1 and MT- 2). Studies in our laboratory and other laboratories have shown that MT expression is dramatically reduced or abolished in primary hepatocellular carcinomas of different etiology. Transgenic mice overexpressing MT are known to exhibit significantly reduced severity of Hepatitis C viral antigen-induced pathogenesis. Our hypothesis is that down regulation of MT renders hepatocytes vulnerable to neoplastic transformation and may be an essential prerequisite for hepatocarcinogenesis. The specific aims of this proposal are to (1) Elucidate the role of metallothionein in chemical (DEN/PB)-induced hepatocarcinogenesis (a well established mouse model system to study hepatocellular carcinoma) using MT knockout and MT overexpressor mice along with genetically matched control animals as the experimental model system and (2) study the molecular mechanism by which C/EBPa, a target of PI3 kinase, regulates MT gene expression in the liver. It is hoped that this study will address the role of metallothionein in the etiology of hepatocarcinogenesis and suppression of its expression as a diagnostic marker for the early detection of liver cancer. Further, elucidation of the molecular mechanism of its suppression during hepatocarcinogenesis should reveal at least one of the important pathways in the malignant transformation of hepatocytes. This proposal also fits well with the mission/goals of multiple institutes and is consistent with the program announcement on etiology, prevention and treatment of hepatocellular carcinomas. Liver cancer results in nearly 15,000 deaths yearly and is one of the few cancers that is increasing in frequency and mortality (particularly in men) in the United States. The present study will address the role of metallothionein in the etiology of liver cancer and suppression of its expression as a diagnostic marker for the early detection of this cancer. Further, elucidation of the molecular mechanism of its suppression should reveal at least one of the important pathways in the malignant transformation of hepatocytes. This proposal also fits well with the mission/goals of multiple institutes (NCI, NIDK, NIAA) and is consistent with the program announcement on etiology, prevention and treatment of hepatocellular carcinomas. [unreadable] [unreadable] [unreadable]